1. Field
Exemplary embodiments of the present invention relate to a substrate recycling method and a recycled substrate, and more particularly, to a method of recycling a growth substrate separated from an epitaxial layer, and a recycled growth substrate.
2. Discussion of the Background
After an epitaxial layer is grown on a substrate, the substrate may be separated from the epitaxial layer. For example, a vertical gallium nitride-based light emitting diode may be prepared by growing an epitaxial layer including n-type and p-type semiconductor layers on a growth substrate, followed by separating the growth substrate from the semiconductor layers. Luminous efficacy of the light emitting diode may be improved by attaching a support substrate having higher thermal conductivity than the growth substrate.
A light emitting diode may be manufactured by a technique, in which a growth substrate is used for growth of epitaxial layers, a support substrate distinguished from the growth substrate is attached to the epitaxial layers in consideration of operating characteristics of the light emitting diode, and the growth substrate is separated from the epitaxial layers. The growth substrate may be separated from the epitaxial layers by, for example, laser lift-off, chemical lift-off, thermal or mechanical lift-off, and the like.
The separated growth substrate may be reused as a substrate for growth of another epitaxial layer, thereby reducing manufacturing cost.
In order to reuse the substrate separated from the epitaxial layer, the separated substrate may be subjected to surface planarization. Chemical-mechanical polishing may be used for surface planarization. However, since a substrate used for growth of a gallium nitride-based semiconductor layer or the gallium nitride-based semiconductor layer grown thereon may have a high hardness, it may be difficult to achieve a desired level of surface planarization through chemical-mechanical polishing. As a result, the surface of the substrate subjected to chemical-mechanical polishing may include scratches, causing cracking.
Moreover, when a gallium nitride-based semiconductor layer remains on an initial substrate used as a growth substrate, the remaining gallium nitride-based semiconductor layer may break upon chemical-mechanical polishing. Thus, it may be difficult to determine suitable process conditions.
The gallium nitride-based semiconductor layer remaining on the substrate may be completely removed through decomposition by heating to a high temperature. However, this process may increase manufacturing costs due to heating of the grown gallium nitride-based semiconductor layer to high temperature. Moreover, when an initial substrate is a gallium nitride substrate, the initial substrate may be damaged. Therefore, it may be difficult to apply the technique of high temperature decomposition in practice.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.